An aircraft weather radar system emits a pulsed signal, or a series of pulsed signals, in a predefined direction (azimuth) from its antenna. When the pulsed signal is incident on weather that lies along the direction of the emitted pulsed signal, a portion of the pulsed signal is reflected back from precipitation within the weather. The radar antenna detects the returned radar signal. Analysis of the received radar signal permits determination of the distance, or range, of the weather from the radar system.
The intensity of the reflectivity information in the received radar signal may be used to determine characteristics of the weather. Reflectivity information is determined as the result of the processing of raw radar return data. Reflectivity information may include normalized return power estimates, return level statistics such as standard deviation, variance, autocorrelation and higher order moments and Doppler frequency statistics such as mean value, standard deviation, variance and other higher order moments. The processed reflectivity information may be referenced as a function of location, either relative to aircraft position or with respect to earth coordinates, and/or may be referenced as a function of altitude, either relative to the aircraft or with respect to the earth. A relatively weak intensity may be associated with light precipitation, such as a light rain or the like. A relatively stronger intensity may be associated with heavier precipitation, such as a heavy rain or the like. And, a very strong intensity may be associated with very heavy precipitation that may present a hazard to the aircraft.
The aircraft weather radar system processes the received data and presents an image corresponding to the weather to the crew on a display. The display indicates the range of the weather by illustrating a plurality of range lines or the like on the display to indicate the relative position of the weather from the aircraft. A colored area displayed on the display indicates the lateral extent of the weather (width and depth of the detected weather).
Various color schemes may be used to indicate characteristics of the detected weather based upon the intensity of the received radar returns. For example, a green colored area may be used to indicate a region of relatively light precipitation (as determined by the relatively weak weather radar reflectivity intensities), a yellow colored area may be used to indicate a region of relatively heavy precipitation (as determined by the relatively stronger weather radar reflectivity intensities), and a red colored area may be used to indicate a region of very heavy, and potentially hazardous, precipitation (as determined by the very strong weather radar reflectivity intensities).
Some types of aircraft weather radar systems, and/or other weather detecting systems, may be able to detect turbulence and/or other types of weather. To indicate turbulence regions, another color such as magenta, may be superimposed on the image. Thus, the crew of the aircraft is able to identify the location of the turbulence relative to the aircraft, and adjust the planned flight path as needed to avoid weather that might be potentially hazardous to the aircraft.
However, the above-described aircraft weather radar systems are not particularly sophisticated in providing analyzed information to the crew. For example, radar intensities in the above example are categorized into three ranges; light, moderate, and heavy (thus generating the green, yellow, and red colored areas on the display). A fourth colored magenta area indicates turbulence. Thus, the aircraft's electronic system applies a relatively simple weather model to analyze the received data. Here, the weather model may be categorized as parsing the weather information into one of five categories (wherein no radar return intensity is shown as a black region, wherein a weak radar return intensity corresponding to relatively light precipitation is shown as a green region, wherein a moderate radar return intensity corresponding to relatively heavy precipitation is shown as a yellow region, wherein a very strong radar return intensity corresponding to potentially hazardous precipitation is shown as a red region, and wherein turbulence is shown as a magenta region).
Further, such simplistic weather models used by such aircraft weather radar systems may not always present the most reliable and useful information to the crew. Characteristics of weather are known to vary based upon geographic location. For example, a storm cell over the Rocky Mountains is quite different from a storm cell over Kansas or the Pacific ocean. Yet the conventional aircraft weather radar system is not able to differentiate between characteristics of the storm based on geography. The conventional aircraft weather radar system simply presents colored regions on the display corresponding to the detected intensity of the received radar returns.
Some aircraft weather radar systems are configured to adjust the intensity ranges of the received radar returns to account for different geographies. For example, U.S. Pat. No. 7,486,319 to Woodell et al., which is incorporated herein by reference in its entirety, adapts the aircraft weather radar system in accordance with a seasonal parameter, a time-of-day parameter, or a location parameter. Radar returns are normalized depending on the environment in which it is detected.
However, the nature of the weather model in the U.S. Pat. No. 7,486,319 to Woodell et al. remains relatively simple. For example, the crew will not be able to immediately discern weather or not the storm cell is growing or decaying by viewing the radar system display. The crew will have to observe the displayed image on their radar system over some period of time to discern such changes in the weather. This requires the crew to periodically observe the radar display, thus increasing the “heads down time” of the crew.
Further, based upon experience, the crew may suspect that there is lightning, hail or the like in the weather. Subjectively interpreting the radar images by the crew increases the “cognitive work load” placed on the crew.
Based on their interpretation of the radar images, the crew may elect to alter their flight plan to avoid weather that they think may be potentially hazardous. The deviation from the flight plan typically adds additional air time and mileage to travel to the destination, thus increasing fuel costs. However, even though the radar image led the crew of the aircraft to conclude that the weather was potentially hazardous, it may be that the weather was, in fact, not hazardous and was safe to travel through.
It would be desirable to provide an improved aircraft weather radar system that increases the crew's “heads up” time and decreases the crew's “cognitive work load.” That is, it would be desirable to provide the crew more time to view where they are going and/or to allow the crew to concentrate on other matters. Further, it is desirable to avoid unnecessary flight plan deviations around weather that is not actually hazardous.